Previous studies and speculation involving the behavior of Roundup Ready soybean under glyphosate application requires further investigations to clarify this issue. This study aimed to evaluate the agronomic performance and oil and protein contents of transgenic soybean culture under glyphosate application. Thus, an assay was carried out in a completely randomized block design, with four replications. Treatments consisted of foliar sprays in increasing doses of glyphosate applied at stages V6 and R2. The variables evaluated were: plant height, number of pods per plant, thousand grain weight and yield, as well as oil and protein contents. It was verified that glyphosate, especially when used in R2, can compromise both the agronomic performance and protein contents.